Filters which are used to remove contaminants from a fluid frequently include a filter element which is mounted in a housing. The filter element includes a filter media. The fluid flows through the filter media so that contaminants in the fluid are retained in the media. The housing includes an inlet through which the fluid is supplied to the filter element, and an outlet through which the fluid can be discharged from the filter after it has been filtered by flowing through the filter media. The material of the filter media is selected according to the nature of the fluid, the nature of the contaminants, and the operating conditions of the filter.
The filter element can include at least one end fitting. Such end fittings are sometimes also referred to as end caps. The filter media can be fastened to the end fitting. Frequently, the filter element will be generally cylindrical with a wall that is provided by the filter media so that a fluid which is to be filtered flows through the wall, either from inside to outside, or from outside to inside. An end fitting can be provided at one or at each of the ends of the cylindrical wall. An end fitting can provide features by which the filter element is located within the filter housing. An end fitting can be fastened to the filter media using an adhesive, or by a welding technique which involves causing the material of the end cap or the media or both to fuse, as is well known. An end fitting can have a groove in which the end of the filter media can be received and fastened. A filter element can include an end fitting at each end. End fittings at opposite ends of a filter element can have different features. For example, features on an end fitting at one end of a filter element for locating the filter element within a filter housing might be omitted from the end fitting at the opposite end of the element.
It is common for a filter element to be capable of being removed from the housing for replacement, in particular when its capacity to absorb contaminants is limited. It is generally important for efficient operation of the filter that the filter element is located securely within the housing and that seals are created reliably between corresponding surfaces of the filter element and the housing to ensure that the fluid which is to be filtered is not able to flow between the inlet and outlet in the housing without having to flow through the filter media.
A filter element can be secured within a housing by means of cooperating threads on the element and the housing. Threads can be provided on an external surface of the filter element and an internal surface of the housing. The threads on an external surface of the filter element can be provided on an end fitting of the element.